The Moon is about 3,475 km across, or about 2,159 miles in diameter, which is roughly one-quarter the width of Earth. It’s also the fifth-largest moon in the Solar System and has a mass of about 7.35 × 10^22 kg.

Quick Scoop

  • Diameter: 3,475 km (2,159 miles)
  • Radius: about 1,737.5 km (1,079.6 miles)
  • Surface area: about 38 million square km (14.6 million square miles)
  • Mass: about 7.35 × 10^22 kg
  • Compared with Earth: about 27% of Earth’s diameter

If you want, I can also give you a simple Earth-vs-Moon size comparison in one line.